Turner Designs TD-700, Operating Manual, Page: 52 / 55

TD-700 Laboratory Fluorometer Operating Manual
Page 51
APPENDIX 11
Principles of Fluorescence
Fluorescence is a physical property of certain atoms and molecules. It is a
molecule's ability to absorb light energy at one wavelength, then instantaneously
re-emit light energy of another, usually longer, wavelength. Each compound that
fluoresces has a characteristic excitation wavelength, (the wavelength of light
that it absorbs) and a characteristic emission wavelength, (the wavelength of light
that it emits when the molecules relax and return to their ground state). These
excitation and emission wavelengths, (or spectra), are often referred to as the
compound's fluorescence signature. Figure 2 shows the key components of a
filter fluorometer.
Figure 2: Principles of Filter Fluorometry
Lamp: The lamp or light source provides the light energy that "excites" the
compound of interest. The lamp actually provides a broader range of light than
that which excites the compound. This broad light range is illustrated by the
"many wavelengths of light" shown in Figure 2.
Lamp
Many wavelengths of light
Excitation Filter
Specific wavelengths of light
Cuvette or
Sample Cell
Emission Filter
Light Detector
Digital Readout
Wavelengths specific to compound
Wavelengths created by
compound, plus stray light